Many Bothans died to obtain this information...oops....wrong universe. Anyway, this information was obtained with great difficulty and under conditions of great danger. (Heck no, not to me, you think I'd put MY life on the line for something like this? Moron....) So, in a nutshell, here it is. The Cassians weren't happy with the way things were. Most of them were much too noble to get involved in a fight where THEY might get a scratch or two. The Mechari were good tacticians and pretty creative, but not always able to anticipate what the "wild" humans would do. The Drakons were excellent fighters but not all that intelligent. So the Cassians came up with an idea. They took DNA from some captive wild humans (ie. Exiles) and some from the Draken. (Yes, that is why the Chua have those lizard looking tails.) They deleted sex chromosomes - no way would they want another inferior race breeding and possibly rising to challenge them. After a few years of tinkering they came up with the ideal creation, sort of. The steroids they had to use to suppress the immune systems of the new organisms made the rather short and gave them something similar to fetal-alcohol syndrome. You know irritable, impulsive, that sort of thing. So we now have the Chua. Genderless, violent, explosive (literally much of the time), very creative, and unable to reproduce. Just in time to turn them loose on Nexus and the Exile fodder trying to push their way on to a world that clearly belonged to the Dominion.